Typically, a removable ink cartridge is mounted in ink jet type printers. A detection section such as a prism for optically detecting the remaining state of ink in the inner portion is provided in some ink cartridges. Since it is possible to remove the ink cartridge, it is necessary to reliably perform mounting in a defined position and to detect the remaining state of the ink at the correct position when the ink cartridge is mounted in the printer. For example, in Japanese Laid-open Patent Application Publication No. 2010-23458, as shown in FIG. 14, an ink cartridge 1J is rotated and mounted with a first engagement section 21J as the center of rotation. Then, a position aligning pin 170J and the inside of a position aligning hole 70J are brought into contact and the positional alignment of the ink cartridge 1J is performed by receiving a repulsive force in the direction of an arrow J using a support member 30J which is able to displace the ink cartridge 1J. As a result, a remaining amount detecting sensor 161J of the printer opposes a prism 60J as the detection section with high precision, and it is possible to accurately perform detection of the remaining state of the ink in the ink cartridge.